210.42 Hz is the frequency of the Moon, calculated from its synodic period — the 29.5-day cycle from new moon to new moon. The Moon has been humanity's most intimate celestial companion since the beginning of consciousness, governing tides, fertility cycles, agricultural rhythms, and the deep currents of emotional life.

In sound healing, the Moon frequency is associated with the inner world — emotions, intuition, dreams, and the subconscious. It is considered a deeply feminine energy (in the archetypal rather than gendered sense), connected to receptivity, nurturing, and the cyclical nature of growth and release.

Practitioners use 210.42 Hz for emotional processing, dream work, and accessing buried feelings that need acknowledgement. It is particularly popular during new moon and full moon meditations, where the intention is to align personal rhythms with the lunar cycle.